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e497c518 GBY |
1 | // SPDX-License-Identifier: GPL-2.0 |
2 | ||
3 | /* | |
4 | * OFB: Output FeedBack mode | |
5 | * | |
6 | * Copyright (C) 2018 ARM Limited or its affiliates. | |
7 | * All rights reserved. | |
e497c518 GBY |
8 | */ |
9 | ||
10 | #include <crypto/algapi.h> | |
11 | #include <crypto/internal/skcipher.h> | |
12 | #include <linux/err.h> | |
13 | #include <linux/init.h> | |
14 | #include <linux/kernel.h> | |
15 | #include <linux/module.h> | |
e497c518 | 16 | |
b3e3e2db | 17 | static int crypto_ofb_crypt(struct skcipher_request *req) |
e497c518 | 18 | { |
e497c518 | 19 | struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); |
21f3ca6c | 20 | struct crypto_cipher *cipher = skcipher_cipher_simple(tfm); |
b3e3e2db EB |
21 | const unsigned int bsize = crypto_cipher_blocksize(cipher); |
22 | struct skcipher_walk walk; | |
23 | int err; | |
e497c518 | 24 | |
b3e3e2db | 25 | err = skcipher_walk_virt(&walk, req, false); |
e497c518 | 26 | |
b3e3e2db EB |
27 | while (walk.nbytes >= bsize) { |
28 | const u8 *src = walk.src.virt.addr; | |
29 | u8 *dst = walk.dst.virt.addr; | |
30 | u8 * const iv = walk.iv; | |
31 | unsigned int nbytes = walk.nbytes; | |
e497c518 | 32 | |
b3e3e2db EB |
33 | do { |
34 | crypto_cipher_encrypt_one(cipher, iv, iv); | |
35 | crypto_xor_cpy(dst, src, iv, bsize); | |
36 | dst += bsize; | |
37 | src += bsize; | |
38 | } while ((nbytes -= bsize) >= bsize); | |
e497c518 | 39 | |
b3e3e2db EB |
40 | err = skcipher_walk_done(&walk, nbytes); |
41 | } | |
e497c518 | 42 | |
b3e3e2db EB |
43 | if (walk.nbytes) { |
44 | crypto_cipher_encrypt_one(cipher, walk.iv, walk.iv); | |
45 | crypto_xor_cpy(walk.dst.virt.addr, walk.src.virt.addr, walk.iv, | |
46 | walk.nbytes); | |
47 | err = skcipher_walk_done(&walk, 0); | |
48 | } | |
49 | return err; | |
e497c518 GBY |
50 | } |
51 | ||
e497c518 GBY |
52 | static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb) |
53 | { | |
54 | struct skcipher_instance *inst; | |
e497c518 | 55 | struct crypto_alg *alg; |
e497c518 GBY |
56 | int err; |
57 | ||
21f3ca6c EB |
58 | inst = skcipher_alloc_instance_simple(tmpl, tb, &alg); |
59 | if (IS_ERR(inst)) | |
60 | return PTR_ERR(inst); | |
e497c518 | 61 | |
b3e3e2db EB |
62 | /* OFB mode is a stream cipher. */ |
63 | inst->alg.base.cra_blocksize = 1; | |
64 | ||
65 | /* | |
66 | * To simplify the implementation, configure the skcipher walk to only | |
67 | * give a partial block at the very end, never earlier. | |
68 | */ | |
69 | inst->alg.chunksize = alg->cra_blocksize; | |
70 | ||
b3e3e2db EB |
71 | inst->alg.encrypt = crypto_ofb_crypt; |
72 | inst->alg.decrypt = crypto_ofb_crypt; | |
e497c518 | 73 | |
e497c518 GBY |
74 | err = skcipher_register_instance(tmpl, inst); |
75 | if (err) | |
21f3ca6c | 76 | inst->free(inst); |
e497c518 | 77 | |
21f3ca6c | 78 | crypto_mod_put(alg); |
e497c518 | 79 | return err; |
e497c518 GBY |
80 | } |
81 | ||
82 | static struct crypto_template crypto_ofb_tmpl = { | |
83 | .name = "ofb", | |
84 | .create = crypto_ofb_create, | |
85 | .module = THIS_MODULE, | |
86 | }; | |
87 | ||
88 | static int __init crypto_ofb_module_init(void) | |
89 | { | |
90 | return crypto_register_template(&crypto_ofb_tmpl); | |
91 | } | |
92 | ||
93 | static void __exit crypto_ofb_module_exit(void) | |
94 | { | |
95 | crypto_unregister_template(&crypto_ofb_tmpl); | |
96 | } | |
97 | ||
c4741b23 | 98 | subsys_initcall(crypto_ofb_module_init); |
e497c518 GBY |
99 | module_exit(crypto_ofb_module_exit); |
100 | ||
101 | MODULE_LICENSE("GPL"); | |
21f3ca6c | 102 | MODULE_DESCRIPTION("OFB block cipher mode of operation"); |
e497c518 | 103 | MODULE_ALIAS_CRYPTO("ofb"); |